The overall aim of the proposed research is to improve the prospects for therapeutic gene transfer in Duchenne muscular dystrophy by addressing two essential rate-limiting issues: immunity to the transgene product and vector delivery. Using a newly described canine animal model for Duchenne muscular dystrophy, the German Short Haired Pointer, the experimental design takes advantage of a deletion of the dystrophin gene to evaluate the comparative immunogenicity of dystrophin and utrophin. We make exclusive use of rAAV vectors. The experimental design tests the hypothesis that in the context of the deletion, recombinant (canine) mini-dystrophin will elicit a deleterious cellular immune response. It further tests the hypothesis that substitution of a similarly designed canine mini-utrophin transgene will circumvent this immune response. Based on extensive preliminary data, the proposal also addresses the hypothesis that the endothelial barrier to systemic gene delivery can be bypassed by temporarily infusing histamine during a period of mechanical circulatory support. We propose a graded series of experiments to address the latter hypothesis, starting with isolated limb perfusion and culminating in systemic gene delivery. These studies will also make extensive use of another naturally occurring animal model, the hamster model for limb-girdle muscular dystrophy. Successful completion of the experimental plan will provide general information relevant to the immunological response to somatic gene delivery and the preservation of organ function during profound but rapidly reversible alterations in endothelial integrity. It will also provide specific information about the rational design of strategies for systemic gene therapy in one of the most common single-gene lethal diseases in man, Duchenne Muscular Dystrophy.